Power management for a portable electronic device

ABSTRACT

A system for a supplemental power source for a hand held portable electronic device is provided. A super capacitor is connected in parallel to a main battery of the portable electronic device. When the main battery becomes disconnected, the super capacitor is used to power the portable electronic device. The super capacitor is also used to provide compensation for the internal impedance of the main battery and the path impedance between the main battery and the load.

FIELD OF THE INVENTION

The present invention generally relates to portable electronic devices.In particular, the present invention relates to a system and method forpower management in a portable electronic device.

BACKGROUND OF THE INVENTION

Portable electronic devices (e.g, notebook computers, mobile dataterminals, radio frequency portable communication devices, etc.)typically include a rechargeable or alkaline battery to supply power tothe portable device. These devices also typically employ a secondarypower source to ensure that data stored in a Random Access Memory (RAM)device is not lost in the event that the main battery becomesdisconnected from the portable device. The main battery may becomedisconnected if the portable electronic device is dropped, or if themain battery is being swapped with a new main battery. The bridgebattery is usually a smaller battery because during a battery swap, theportable device normally will enter a low current or suspend mode, sothat most current drawn from the bridge battery is used to refresh theRAM device, until a new main battery is installed into the device.

Many portable devices employ complicated switching or logic circuitrywhen changing from the main battery power to the bridge battery power.The switching or logic circuitry takes up valuable space on a circuitboard that could be utilized to perform the functions of the portabledevice. In some cases, additional circuit boards are necessary to housethe switching or logic circuitry. Furthermore, some of these portabledevices employ expensive power management and supervisory circuitry tocause the functional components in the portable device to enterdifferent modes, depending on the type of unit powering the portabledevice or the current status of the unit powering the portable device.The additional power management and supervisory circuitry adds to thesize, the cost and also to the complexity of the portable device.

Accordingly, there is a strong need in the art for a system and/ormethods that can provide power distribution for a portable electronicdevice at low cost, while reducing space utilized in employing such asystem.

SUMMARY OF THE INVENTION

The following presents a simplified summary of the invention in order toprovide a basic understanding of some aspects of the invention. Thissummary is not an extensive overview of the invention. It is intended toneither identify key or critical elements of the invention nor delineatethe scope of the invention. Its sole purpose is to present some conceptsof the invention in a simplified form as a prelude to the more detaileddescription that is presented later.

The present invention relates to a power management system for aportable electronic device. The power management system providessupplemental power to the portable electronic device in the event thatthe main battery becomes disconnected from the portable electronicdevice. Thus, in accordance with one aspect of the present invention, apower management system is provided for a portable electronic devicethat includes a battery and a super capacitor electrically connected tothe battery. The super capacitor is employed to provide power to theportable electronic device power supply when the battery losesconnection with battery contacts.

In accordance with another aspect of the present invention, a system isprovided for compensating the internal impedance of a battery in aportable electronic device. When the internal impedance of a batteryrises to a predetermined level, the low internal impedance of a supercapacitor is employed to compensate for the battery's high internalimpedance, thus preventing a voltage drop in the system.

In accordance with another aspect of the present invention, a system isprovided in which a battery and a super capacitor share a load. Thebattery and the super capacitor are connected electrically in paralleland are able to drive a common load while distributing the demand placedon the battery and super capacitor in accordance with their respectivecapacity and power capabilities.

In accordance with yet another aspect of the present invention a methodis provided for supplementing a power source for a portable electronicdevice. The method includes: providing a battery to the device, thebattery being employed to power the device as long as the batteryremains connected to the device, and providing a super capacitor to thedevice. The super capacitor is employed in the event that the batterybecomes disconnected from the device and/or the ability of the batteryto provide a suitable level of power to the device is diminished.

In accordance with yet another aspect of the present invention, a methodis provided for compensating the internal impedance of a battery in aportable electronic device. The method includes, providing a battery tothe device as a main power supply and providing a super capacitorelectrically connected to the battery, the super capacitor beingoperable to balance the internal impedance of the battery. As theinternal impedance of the battery rises, the low level of the internalimpedance in the super capacitor balances out the high internalimpedance of the battery to prevent a voltage drop out in the system.

To the accomplishment of the foregoing and related ends, the inventionthen, comprises the features hereinafter fully described andparticularly pointed out in the claims. The following description andthe annexed drawings set forth in detail certain illustrative aspects ofthe invention. These aspects are indicative, however, of but a few ofthe various ways in which the principles of the invention may beemployed and the present invention is intended to include all suchaspects and their equivalents. Other objects, advantages and novelfeatures of the invention will become apparent from the followingdetailed description of the invention when considered in conjunctionwith the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram of a power management system for aportable electronic device in accordance with one aspect of the presentinvention;

FIG. 2 is a schematic block diagram of a power management system for aportable electronic device in accordance with one aspect of the presentinvention;

FIG. 3 is a schematic block diagram of a power management system for aportable electronic device in accordance with one aspect of the presentinvention;

FIG. 4 is a perspective front view of a portable electronic device inaccordance with one aspect of the present invention;

FIG. 5 is a perspective back view of a portable electronic device inaccordance with one aspect of the present invention; and

FIG. 6 is a schematic block diagram of a general operation of a portableelectronic device in accordance with one aspect of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will now be described with reference to thedrawings, wherein like reference numerals are used to refer to likeelements throughout.

Referring initially to FIG. 1, a schematic block diagram of a powermanagement system 5 for a portable electronic device is provided inaccordance with one aspect of the present invention. In this example,the portable electronic device is a hand-held terminal 10 used in awireless communication network for tracking inventory, storing data,etc. A battery 20 is coupled to the hand-held terminal 10 and isemployed to provide power to the hand-held terminal 10. The battery 20is typically a rechargeable Lithium-Ion battery. However, it is to beappreciated that the battery 20 may be of any type (e.g.,Nickel-Cadmium, Nickel-Metal-Hydride, Alkaline, Lithium Polymer),depending upon the application at hand. If the battery 20 ceases toprovide power to the hand-held terminal 10, a super capacitor 30 isemployed as a supplemental power source to avoid information loss in thehand-held terminal 10. The super capacitor 30 and the battery 20 areconnected electrically in parallel. The battery 20 may cease to providepower in a number of different situations; for example, the battery 20may become disconnected if the terminal 10 is dropped, when the battery20 is being replaced with a new battery, or if the battery 20 fails.However, it is to be appreciated that the super capacitor 30 is alsoemployed by the system in normal operating conditions of the hand-heldterminal 10, as will be described in further detail below. An inrushcurrent limiter 40 can also be included in the system to protect thebattery from a high peak surge or inrush currents caused by a fullydepleted supercap.

In FIG. 2, a schematic block diagram of a hand-held mobile terminal 45,which includes a power management system, is shown in accordance withanother aspect of the present invention. A battery 50 is connected to ahand-held mobile terminal 45 via battery contacts 70 and 80. The battery50 includes electrical contacts designed to correspond to the batterycontacts 70 and 80 of the hand-held terminal 45. The contacts areemployed to provide power from the battery 50 to the terminal 45.Preferably, the contacts of the battery 50 and the hand-held terminal 45are made of a highly conductive metal that is resistant to corrosion,such as, for example, Nickel Plated Beryllium Copper. When theelectrical contacts of the battery 50 are connected to the batterycontacts 70 and 80 of the hand-held terminal 45, power is provided to aregulator 90 of the hand-held terminal 45. The regulator 90, in turn,provides power to hand-held terminal load components 60. The terminalload components 60 include, but are not limited to, a microprocessor100, Random Access Memory (RAM) and Read Only Memory (ROM), a radio 110,which receives power through the regulator, a radio 111, which receivespower directly from the battery 50 and/or super capacitor 130 andperipherals 120. Radio 111 is connected directly to the battery 50and/or super capacitor 130 instead of through the regulator 90 becauseit requires more power than the regulator 90 can provide. Radio 111 mayreceive and transmit through a LAN, GSM, CDPD, GPRS, PAN,or CDMA, forexample. If the battery 50 loses connection with the battery contacts 70and 80, the battery 50 will cease to provide energy to the regulator 90.Therefore, supplemental power for the mobile terminal 45 is needed toavoid information loss.

The hand-held mobile terminal 45, thus, includes a super capacitor 130connected in parallel with the battery 50. The large capacitance ofsuper capacitors permits the storage of relatively large amounts ofenergy. Thus, the stored energy in the super capacitor 130 can be usedto power the hand-held terminal load components 60 for a short period oftime when the battery 50 is not connected to the terminal 45, orotherwise ceases to provide energy to the terminal 45. Super capacitorsare typically high surface area carbon capacitors and similarhigh-energy storage devices. They are able to hold a very high charge,which can be released very quickly or rather, more slowly, dependingupon the situation needed. Batteries, generally, have limitedcapabilities to deliver power and traditional capacitors have limitedcapabilities to store energy, while super capacitors are able to combinesome of the energy storage capabilities of batteries and power dischargecharacteristics of capacitors. The operating principle of a supercapacitor is based on an electric double layer positioned at theinterface between activated carbon particles and sulfuric acid solutionas electrolyte. An ionically conducting but electrically insulatingporous membrane separates the two electrodes. Charge iselectrostatically stored in the electrochemical double-layer formed onthe carbon surface of the super capacitor. Conductive rubber membranescontain the electrode and electrolyte material and make contact to thecell.

One instance in which the battery 50 can lose connection with thebattery contacts 70 and 80 is if the hand-held terminal 45 is dropped.The drop of the hand-held terminal 45 does not affect the supercapacitor 130 as it is securely attached to the regulator 90electronics. Since the super capacitor 130 is connected directly to theregulator 90, the super capacitor 130 expends its stored energy tomaintain power to the regulator 90 and the terminal architecture of thehand-held terminal 45 until the battery 50 reconnects with the batterycontacts 70 and 80. It is to be appreciated that the super capacitor 130can be used as a supplemental power source in any situation in which thebattery 50 becomes disconnected with the hand-held terminal 45, orotherwise fails to provide a suitable level of power to the terminal 45.

Thus, the hand-held terminal 45 may utilize the super capacitor 130 asthe main source of power for a short period of time. High initialcurrents can result due to super capacitor impedance when large voltagedifferences are between the capacitor and battery are present. Theselarge super capacitors act like a short circuit, producing an immediateinrush surge current with a fast rise time. The peak inrush current isseveral orders of magnitude greater than the circuit's steady statecurrent. This power surge can lead to the activation of a batteryprotection circuit if the battery fails and/or can seriously damageother components or lead to blown fuses or tripped breakers. Thus, aninrush current limiter 140 is connected in series with the supercapacitor 130. Inrush current limiter 140 is designed to limit theinrush level to the capacitor without a current limit on the output fromthe capacitor. Inrush current.limiter 140 may be a NTC (NegativeTemperature Coefficient) thermistor or an active circuit. However, anyappropriate inrush current suppression technique may be employeddepending upon the application, the type of battery employed, theequipment's power level, and the frequency at which the equipment islikely to be exposed to inrush currents.

In addition to acting as a supplemental power source for the battery 50,the super capacitor 130 shares a common load with the battery 50, whichextends the operating time of a hand-held terminal. The super capacitor130 and the battery 50 are connected electrically in parallel to drivethe load. Furthermore, the system is able to distribute the demandsplaced upon the super capacitor 130 and the battery 50 in accordancewith their individual capacity and/or power capabilities. The presentinvention also aids to tap more of the available capacity of the batterybetween recharges.

Turning now to FIG. 3, the stored energy in a super capacitor 150 can beused during high power demand periods to provide compensation for theinternal impedance of a battery 155 and the path impedance between thebattery 155 and the load. The internal resistance of current batterytechnology varies with temperature and percent charge. In the battery155, the change in impedance due to a change in temperature isrepresented by Z_(A); and the change in impedance due to a change incharge is represented by Z_(B). For example, as temperature drops, theimpedance in the battery rises. This temperature drop combined with alarge power demand from the hand-held terminal 45 can result in avoltage drop out of the battery 155. Thus, the super capacitor 150 isconnected electrically in parallel with the battery 155 to compensatefor the rise in the battery's impedance. The super capacitor 150 haslower internal impedance, represented by Z_(C), and more stable internalimpedance over temperature than the battery 155. Thus, at coldtemperatures, when the internal impedance of the battery 155 rises, thesignificantly lower internal impedance of the super capacitor 150 isable to provide compensation for the high internal impedance of thebattery 155, thereby preventing a regulator to prematurely drop out.Similarly, the internal impedance of the super capacitor 150 compensatesthe internal impedance of the battery 155 for a change in charge in thebattery 155 or a combination of a change in temperature and a change incharge in the battery 155. The present invention also enables the powersupply to operate in its peak efficiency range.

Turning now to FIGS. 4 and 5, pictorial representations of front andback views, respectively, of a portable electronic device are shown. Inthis example, the portable electronic device is a hand-held terminal 250used in a wireless communication network for tracking inventory, storingdata, etc. The user may input and/or process data via a keypad, bar codescanner, imager, etc. independent of the hand-held terminal 250 beingconnected to a LAN or WAN, for example. When the hand-held terminal 250does not include a radio to provide for real time communications of datato a LAN or WAN, the data is stored in memory within the hand-heldterminal 250. In such circumstances, when the hand-held terminal 250 iseventually connected to a LAN or WAN, the data can be transmitted to ahost computer (not shown). It will be appreciated that the portabledevice could also be any other device that is portable in nature andhaving electronic circuitry therein in accordance with the presentinvention. For example, the portable device could be a laptop computeror notebook computer, a PDA, or even a cellular telephone or pager,which employs batteries.

The hand-held terminal 250 includes a housing 260, a touch screen 270for displaying information to a user and allowing the user to inputinformation and/or operational commands, a set of user interface keys280 for allowing the user to input information and/or operationalcommands and a bar code reader 290. The bar code reader 290 is adaptedto read information on a bar code label or the like. The hand-heldterminal 250 can include a LED that is illuminated to reflect whetherthe bar code has been properly or improperly read. The describedcomponents 270, 280 and 290 are located in the housing 260 that is anelongated enclosure of a size and includes such contours as toconveniently fit into the open palm of the user. The housing 260 may becomprised of a number of shell portions such as for example front andrear shells 300 and 310 as well as a battery pack lid 320 (FIG. 5). Thehousing 260 may also include a hand strap 330 (FIG. 5) for user comfort.The user interface keys 280 may include a full alphanumeric keypad,function keys, enter keys, etc. The hand-held terminal 250 also includesa window through which a bar code reader 290 is able to read a bar codelabel presented to the hand-held terminal 250. Also included in thehand-held terminal 250 is an ON/OFF power key 340 for turning the deviceon and off.

Turning now to FIG. 6, a schematic representation according to oneaspect of the present invention is shown in which a processor 360 isresponsible for controlling the general operation of a portableelectronic device 350. The processor 360 is programmed to control andoperate the various components within the portable electronic device 350in order to carry out the various functions described herein. Theprocessor or CPU 360 can be any of a plurality of processors, such asthe NEC 4121, NEC 4181, Intel 1110, Intel Pentium 50/75, Intel Pentium60/90, and Intel Pentium 66/100, Intel Pentium PRO and Intel Pentium 2,and other similar and compatible processors or micro controllers. Aprocessor such as Intel's 8 bit microcontrollers, the 8031, 8051 or 8052can be utilized. The manner in which the processor 360 can be programmedto carry out the functions relating to the present invention will bereadily apparent to those having ordinary skill in the art based on thedescription provided herein.

A memory 370 tied to the processor 360 is also included in the portableelectronic device 350 and serves to store program code executed by theprocessor 360 for carrying out operating functions of the portableelectronic device 350 as described herein. The memory 370 also serves asa storage medium for temporarily storing information such as receipttransaction information and the like. The memory 370 is adapted to storea complete set of the information to be displayed. According to apreferred embodiment, the memory 370 has sufficient capacity to storemultiple sets of information, and the processor 360 could include aprogram for alternating or cycling between various sets of displayinformation.

A display 380 is coupled to the processor 360 via a display driversystem 390. The display 380 may be a liquid crystal display (LCD) or thelike. The display 380 is operable to display data or other informationrelating to ordinary operation of the portable electronic device 350.For example, the display 380 may display a set of customer information,which is displayed to the operator and may be transmitted over a systembackbone (not shown). Additionally, the display 380 may display avariety of functions that control the execution of the portableelectronic device 350. The display 380 is capable of displaying bothalphanumeric and graphical characters. Furthermore, the display 380 maybe a touch screen, able to receive user information as well as displayinformation.

Power is provided to the processor 360 and other components forming theportable electronic device 350 by a battery pack 400. In the event thatthe battery pack 400 fails or becomes disconnected from the portableelectronic device 350, a supplemental power source 410 provides power tothe processor 360, the supplemental power source 410 being a supercapacitor connected electrically in parallel with the battery pack 400.The hand-held terminal 350 may enter a minimum current draw of sleepmode upon detection of a battery failure.

The portable electronic device 350 includes a communication subsystem410 that includes a data communication port 420, which is employed tointerface the processor 360 with the main computer. The portableelectronic device 350 also optionally includes an RF section 430connected to the processor 360. The RF section 430 includes an RFreceiver 440, which receives RF transmissions from the main computer forexample via an antenna 450 and demodulates the signal to obtain digitalinformation modulated therein. The RF section 430 also includes an RFtransmitter 460 for transmitting information to the main computer, forexample, in response to an operator input at keypad 465 or thecompletion of a transaction. Peripheral devices, such as a printer 470,signature pad 480, magnetic stripe reader 490, touch panel 500, andbarcode scanner 510 can also be coupled to the portable electronicdevice 350 through the processor 360.

It will be appreciated that the scope of the present invention isintended to include any portable electronic device and the type ofbattery it is employing. A super capacitor applies an appropriate levelof power to the portable electronic device so that the device mayoperate while the battery is not connected to the battery contacts.

Although the invention has been shown and described with respect to acertain preferred aspect or aspects, equivalent alterations andmodifications will occur to others skilled in the art upon reading andunderstanding this specification and the annexed drawings. In particularregard to the various functions performed by the above describedcomponents (systems, assemblies, systems, etc.), the terms used todescribe such components are intended to correspond, unless otherwiseindicated, to any component which performs the specified function of thedescribed component (e.g., that is functionally equivalent), even thoughnot structurally equivalent to the disclosed structure which performsthe function in the herein illustrated exemplary aspect or aspects ofthe invention. In addition, while a particular feature of the inventionmay have been described above with respect to only one of severalaspects, such feature may be combined with one or more other features ofthe other aspects, as may be desired and advantageous for any given orparticular application. Furthermore, to the extent that the term“includes” is used in either the detailed description or the claims,such term is intended to be inclusive in a manner similar to the term“comprising”.

What is claimed is:
 1. A system for providing a supplemental powersupply to a portable electronic device, comprising: a battery connectedto a portable electronic device through battery contacts; a device powersupply, the device power supply being supplied power by the battery; asuper capacitor employed to provide power to the device power supplywhen the battery loses connection with the battery contacts; and aninrush current limiter electrically connected to the super capacitor. 2.The system of claim 1, the super capacitor being connected electricallyin parallel with the battery.
 3. The system of claim 1, the inrushcurrent limiter being connected electrically in series with the supercapacitor.
 4. The system of claim 1, the device power supply providingpower to load components of the portable electronic device.
 5. Thesystem of claim 4, the portable electronic device load componentsincluding a microprocessor, a radio, and peripherals.
 6. The system ofclaim 1, the battery being rechargeable.
 7. The system of claim 6, thebattery being a lithium-ion battery.
 8. The system of claim 6, thebattery being a nickel-cadmium battery.
 9. The system of claim 6, thebattery being a nickel-metal-hydride battery.
 10. A method for providinga supplemental power supply to a portable electronic device, comprising:providing a battery to a portable electronic device, the batteryproviding power to the portable electronic device through batterycontacts; providing a super capacitor electrically in parallel with thebattery; providing an inrush current limiter electrically in series withthe super capacitor; and employing the super capacitor to provide powerto the portable electronic device when the battery loses connection withthe battery contacts.
 11. A method for providing impedance compensationfor a battery in a portable electronic device, comprising: providing abattery to a portable electronic device, the battery providing power tothe portable electronic device through battery contacts; and providing asuper capacitor electrically in parallel with the battery, the supercapacitor providing internal impedance compensation if an internalimpedance of the battery rises to a predetermined level.
 12. The methodof claim 11, the super capacitor being further employed to provide powerto the portable electronic device when the battery loses connection withthe battery contacts.
 13. A system for a hand-held mobile terminalcomprising: a battery; a super capacitor electrically connected inparallel with the battery, the super capacitor being operable to share acommon load with the battery.
 14. The system of claim 13, the systembeing operable to distribute the demand placed on the battery and supercapacitor in accordance with their respective capacity and powercapabilities.